The present disclosure relates to subject matter contained in Japanese Patent Application No. 10-287391 (filed on Oct. 9, 1998), which is expressly incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a treating instrument for an endoscope in which the proximal end of a flexible sheath is connected to an operating part.
2. Description of the Prior Art
As the flexible sheath of a treating instrument for an endoscope, a coil pipe that is formed by close-winding a thin stainless steel wire with a uniform diameter or a tetrafluoroethylene resin tube (Teflon TM tube) is widely used. The proximal end of the flexible sheath is connected to an operating part.
Normally, the flexible sheath does not buckle even if it is bent with a considerably small radius of curvature. However, if the flexible sheath is bent in the vicinity of the joint between the flexible sheath and the operating part, which is a rigid body, the flexible sheath often buckles and breaks easily because of a sharp change in the state of bending.
To prevent the flexible sheath from buckling, the proximal end portion of the flexible sheath is generally covered with a buckling preventing member formed from a tetrafluoroethylene resin tube or a close-wound coil tube, for example.
If the buckling strength (resistance to an external force applied in the bending direction) of the abovedescribed buckling preventing member is set excessively strong, the flexible sheath is likely to buckle at the boundary between the sheath and the buckling preventing member. Therefore, it is preferable to set the buckling strength of the buckling preventing member roughly in the range of from several times to 10 times as high as the buckling strength of the flexible sheath.
However, the sheath of the treating instrument is formed to be highly flexible so as not to damage built-in components of the endoscope, such as an optical fiber bundle, when inserted into or removed from the instrument-inserting channel of the endoscope.
Therefore, if the buckling strength of the buckling preventing member is set at a level just suitable for the flexible sheath, the buckling preventing effect may be insufficient at the joint between the flexible sheath and the operating part. Consequently, buckling breakage is likely to occur.